iDEFENSE Security Advisory 02.17.04

Ipswitch IMail LDAP Daemon Remote Buffer Overflow
http://www.idefense.com/application/poi/display?id=74
February 17, 2004

I. BACKGROUND

Ipswitch IMail server is a Windows based messaging solution with a
customer base of over 53 million users. More information about the
application is available at
http://www.ipswitch.com/products/IMail_Server/index.html.

II. DESCRIPTION

Exploitation of a remote buffer overflow within the LDAP daemon of
Ipswitch IMAIL Server allows attackers to execute arbitrary code under
administrator privileges. LDAP messages are comprised of various tags
consisting of an identifier, a length and the content. An integer is
represented in LDAP by the identifier byte 0x02, followed by the length
of the integer in bytes. This is followed by the actual integer itself.
As an example the following tag: 0x02 0x03 0x0A 0x25 0xBD represents the
integer 665,501 (0xA25BD). The problem exists due to insufficient bounds
checking upon copying of user supplied data with large tag lengths to a
stack based buffer. The following assembly instruction can be abused to
overwrite memory addresses as offsets from the current frame pointer
because the attacker has control over ecx and var_4 at the time of
exploitation:

.text:00401188 mov byte ptr [ebp+ecx+var_4], dl

An attacker can utilize this to overwrite the address of the Global
Exception Handler, which can be found at a static distance from the
frame pointer. Overwriting this address with that of a memory location
containing a JMP/CALL ebx instruction (in Windows 2000)
or a POP xxx POP xxx RET instruction (in Windows XP), allows the
attacker to redirect the flow of control to his or her own supplied
code.

III. ANALYSIS

Successful exploitation allows unauthenticated remote attackers to
execute arbitrary code under administrator privileges. Exploitation is
possible across both Windows 2000 and XP platforms. However, it requires
minor changes in order to work.

IV. DETECTION

iDEFENSE has confirmed that the LDAP daemon (iLDAP.exe ver. 3.9.15.10)
shipping with IMail Server version 8.03 is vulnerable. It us suspected
that earlier versions are vulnerable as well.

V. WORKAROUNDS

Disable or firewall the LDAP service (TCP port 389) if unneeded.

VI. RECOVERY

Successful exploitation can cause the LDAP daemon to crash and will
require a restart in order to resume normal operation.

VII. VENDOR RESPONSE

"Testing has completed their review of 8.05 Hotfix 2 and we are ready to
release."

The fix will be available for download at:

http://www.ipswitch.com/support/imail/releases/imail_professional/im805H
F2.html

VIII. CVE INFORMATION

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.

IX. DISCLOSURE TIMELINE

October 31, 2003    Exploit acquired by iDEFENSE
February 2, 2004    Initial vendor notification
February 3, 2004    iDEFENSE clients notified
February 3, 2004    Vendor response received
February 17, 2004   Coordinated public disclosure